Field of Invention
The present invention relates to a prosthetic device for a knee joint, particularly a prosthetic device for a knee joint having a body portion and a keel, and methods of implanting and removing the same.
Description of Related Art
Prosthetic devices for knee joints, e.g., knee implants, typically have structures on the bone interface surface to facilitate attachment of the prosthetic device to the bone of the knee joint. For example, it is common for a prosthetic device to have one or more pegs and a keel extending outwardly from a longitudinal axis or centerline of the bone interface surface. Such a keel typically is large and projects a significant length from the bone interface surface to facilitate connection of the prosthetic device to the bone and to provide sufficient strength and stiffness for the prosthetic device.
The large, central keel of a conventional prosthetic device can create difficulties during implantation. For example, the large keel requires the formation of a deep void in the bone to receive the keel. Forming this deep void can cause bone preparation time to be longer than desired, and require multiple cutting tools. Moreover, the large keel can cause fracture of bone during implantation, such as when the void is not sufficiently wide and/or deep.
The large keel also can create difficulties during revision, e.g., the removal of the prosthetic device from the bone to allow for its replacement with a new prosthetic device. To be able to remove the implanted prosthetic device, a relatively large amount of bone may need to be resected so that the keel may be removed from its deep insertion into the bone. Also, the keel itself may cause removal of a relatively large amount of bone when the prosthetic device is removed from the bone, especially when cement is used to join the keel to the bone.
A conventional prosthetic device may include a rim or lip around most or all of the outer perimeter of the bone interface surface. When the prosthetic device is fit within a void in the bone, the rim can form a pocket that contains the cement to increase cement pressurization and cement interdigitation into the bone to enhance fixation. The rim itself typically does not sufficiently enhance the strength and stiffness of the prosthetic device.
A conventional prosthetic device also may have a bone interface surface that is configured based on resection techniques. For example, bone may be resected by making multiple planar cuts. Accordingly, a conventional bone interface surface can have multiple substantially planar surfaces to fit properly on the bone. The intersection of those substantially planar surfaces can result in thin material cross-sections, concentrating and increasing stresses, which can lead to failure of the prosthetic device. Moreover, because the prosthetic device must be sufficiently thick at the intersection of substantially planar sections to decrease the likelihood of failure, other areas of the prosthetic device may be thicker than necessary, thus requiring more than an optimal amount of bone removal for implantation.